Non-zero dispersion shifted optical fiber

ABSTRACT

An optical waveguide fiber including a central core region extending radially outward from the centerline and having a non-negative relative refractive index percent profile. The optical fiber exhibits an effective area of greater than about 60 μm 2  at a wavelength of about 1550 rm, a dispersion slope of less than 0.07 ps/nm 2 /km at a wavelength of about 1550 nm, and a zero-dispersion wavelength of less than about 1450 nm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119(e)of U.S. Provisional Application Ser. No. 60/546,492 filed on Feb. 20,2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to non-zero dispersion shifted opticalfibers (NZDSF), or NZDS fibers, or NZ-DSF's.

2. Technical Background

Wavelength division multiplexing (WDM) systems have operated around the1550 nm wavelength region, defined herein as including the C-band, whichincludes wavelengths between about 1525 nm to about 1565, and theL-band, which includes wavelengths between about 1565 nm to about 1625nm. Some known fibers have a zero dispersion wavelength located outsidethe operation window which may help prevent nonlinear penalties such asfour-wave mixing (FWM) and cross-phase modulation (XPM). However, thezero dispersion wavelength of known NZDSF fibers is typically within 100nm of 1550 nm in order to reduce the magnitude of the dispersion of atransmitted signal in the 1550 nm operating window so as to allow longerspan lengths and less frequent dispersion compensation.

Preferably, coarse wavelength division multiplexing (CWDM) systems andapplications operate in the WDM 1550 nm window, i.e. in the C-andL-bands, in the S-band (between about 1450 nm and about 1525 run), andin the 1310 nm window (between about 1280 rm and about 1330 nm).

Known fibers have optical characteristics which are suitable foroperation in specific windows. For example, standard single modetransmission fibers, such as the SMF-28™ optical fiber manufactured byComing Incorporated, have a zero dispersion wavelength at or near 1310nm, and such fibers can perform suitably in the 1310 nm window. Thedispersion exhibited by such optical fiber at 1550 nm is around 17ps/nm/km, which is larger than the dispersion at 1550 nm of typicalNZDSF fiber, and which can require frequent dispersion compensation.NZDSF optical fiber can perform suitably in the 1550 nm window. Examplesof NZDSF fiber include: LEAF® fiber by Corning Incorporated which has anaverage zero dispersion wavelength near 1500 nm and a dispersion slopeof about 0.08 ps/nm/km at about 1550 nm, Submarine LEAF® fiber byCorning Incorporated which has an average zero dispersion wavelengthnear 1590 nm and a dispersion slope of about 0.1 ps/nm/km at about 1550nm, MetroCor® fiber by Coming Incorporated which has a zero dispersionwavelength near 1650 nm, and Truewave RS™ fiber by Lucent Corporationwhich has a zero dispersion wavelength of about 1450 nm. However, themagnitude of the dispersion in the 1310 nm window of these NZDSF opticalfibers is not low, and many NZDSF fibers have specified cable cutoffwavelengths which are greater than 1260 nm.

SUMMARY OF THE INVENTION

Disclosed herein is an optical waveguide fiber including a central coreregion extending radially outward from the centerline and having anon-negative relative refractive index percent profile. The opticalfiber exhibits an effective area of greater than about 60 μm² at awavelength of about 1550 nm, a dispersion slope of less than 0.07ps/nm²/km at a wavelength of about 1550 nm, and a zero-dispersionwavelength of less than about 1450 nm, preferably less than 1430 nm,more preferably between 1350 and 1430 nm, even more preferably between1380 and 1420 nm.

In preferred embodiments, the effective area at a wavelength of about1550 nm is greater than about 60 μm², preferably between about 60 μm²and 70 μm², the dispersion at a wavelength of about 1550 nm is between 6and 10 ps/nm-km, more preferably between 7 and 9 ps/nm-km, thedispersion slope at a wavelength of about 1550 nm is less than 0.07ps/nm²/km, more preferably less than 0.06 ps/nm²⁻ km, and thezero-dispersion wavelength is less than about 1450 nm, preferably lessthan 1430 nm, more preferably between 1350 and 1430 nm, even morepreferably between 1380 and 1420 nm.

In preferred embodiments, the optical waveguide fiber comprises acentral core region extending radially outward from the centerline to aradius R₁ and having a positive relative refractive index percent, Δ₁ %(r) with a maximum relative refractive index percent, Δ_(1,MAX), whereinΔ_(1,MAX)>0.6%, a first annular region surrounding the central coreregion and extending to a radius R₂ and having a non-negative relativerefractive index percent, Δ₂ % (r), with a minimum relative refractiveindex percent, Δ_(2,MIN), a second annular region surrounding the firstannular region and extending to a radius R₃ and having a positiverelative refractive index percent, A₃ % (r) with a maximum relativerefractive index percent, Δ_(3,MAX,) and an outer annular claddingregion surrounding the second annular region and having a relativerefractive index percent, Δ_(c) % (r), whereinΔ_(1,MAX)>Δ_(3,MAX)>Δ_(2,MIN)≧0, and wherein the relative refractiveindex of the optical fiber is selected to provide an effective area ofgreater than about 60 μm² at a wavelength of about 1550 nm, anattenuation at a wavelength of about 1550 nm of less than 0.22 dB/km,and a zero-dispersion wavelength of less than about 1450 nm. Preferably,the relative refractive index of the optical fiber is selected toprovide a dispersion slope of less than 0.07 ps/nm²/km at a wavelengthof about 1550 nm, even more preferably less than 0.06 ps/nm²/km at awavelength of about 1550 nm. Preferably, the zero-dispersion wavelengthis less than about 1430 nm, more preferably between about 1350 and 1450nm, even more preferably between about 1350 and 1430 nm. Preferably, theattenuation at a wavelength of about 1550 nm is less than 0.20 dB/km.The optical fiber preferably has a dispersion at a wavelength of about1550 nm of between 6 and 10 ps/nm-km, more preferably between 7 and 9ps/mn-km. Preferably, the central core region extends to a radius ofbetween 3 and 5 μm, the first annular region has a width of betweenabout 3 and 7 μm, and a midpoint of between 5 and 8 μm, the secondannular region has a width of between about 1 and 5 μm, and a midpointof between 10 and 12 μm, wherein the outer annular cladding regionsurrounds and is directly adjacent to the second annular region, whereinthe core ends and the outer annular cladding region begins at R₃, andwherein Δ_(c) % (r)=0.

In some preferred embodiments, the central core region comprises acentermost portion extending from the centerline to a radius of 1 μm,and a second portion surrounding and directly adjacent to the centermostportion, wherein the centermost portion has a maximum relativerefractive index Δ_(AMAX), wherein the second portion has a maximumrelative refractive index Δ_(BMAX), and wherein the absolute magnitudeof the difference between Δ_(AMAX) and Δ_(BMAX) is greater than 0.2%. Inone subset of embodiments, Δ_(AMAX)>Δ_(BMAX). In another set ofembodiments, Δ_(BMAX)>Δ_(AMAX). In other embodiments, the absolutemagnitude of the difference between Δ_(AMAX) and Δ_(BMAX) is greaterthan 0.4%.

Preferably, the core ends and the outer annular cladding region beginsat R₃, wherein R₃ is between 11 and 18 μm.

Preferably the optical fiber described and disclosed herein allowssuitable performance at a plurality of operating wavelength windowsbetween about 1260 nm and about 1650 nm. More preferably, the opticalfiber described and disclosed herein allows suitable performance at aplurality of wavelengths from about 1260 nm to about 1650 nm. In apreferred embodiment, the optical fiber described and disclosed hereinis a dual window fiber which can accommodate operation in at least the1310 nm window and the 1550 nm window.

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-10 show refractive index profiles corresponding to a first setof preferred embodiments of an optical waveguide fiber as disclosedherein.

FIG. 11 shows refractive index profiles corresponding to a second set ofpreferred embodiments of an optical waveguide fiber as disclosed herein.

FIG. 12 shows refractive index profiles corresponding to a third set ofpreferred embodiments of an optical waveguide fiber as disclosed herein.

FIG. 13 shows refractive index profiles corresponding to a fourth set ofpreferred embodiments of an optical waveguide fiber as disclosed herein.

FIG. 14 is a schematic cross-sectional view of a preferred embodiment ofan optical waveguide fiber as disclosed herein.

FIG. 15 is a schematic view of a fiber optic communication systememploying an optical fiber as disclosed herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Additional features and advantages of the invention will be set forth inthe detailed description which follows and will be apparent to thoseskilled in the art from the description or recognized by practicing theinvention as described in the following description together with theclaims and appended drawings.

The “refractive index profile” is the relationship between refractiveindex or relative refractive index and waveguide fiber radius.

The “relative refractive index percent” is defined as Δ%=100×(n_(i)²−n_(c) ²)/2n_(i) ², where n_(i) is the maximum refractive index inregion i, unless otherwise specified, and n_(c) is the averagerefractive index of the cladding region. As used herein, the relativerefractive index is represented by Δ and its values are given in unitsof “%”, unless otherwise specified. In cases where the refractive indexof a region is less than the average refractive index of the claddingregion, the relative index percent is negative and is referred to ashaving a depressed region or depressed index, and is calculated at thepoint at which the relative index is most negative unless otherwisespecified. In cases where the refractive index of a region is greaterthan the average refractive index of the cladding region, the relativeindex percent is positive and the region can be said to be raised or tohave a positive index. An “updopant” is herein considered to be a dopantwhich has a propensity to raise the refractive index relative to pureundoped SiO₂. A “downdopant” is herein considered to be a dopant whichhas a propensity to lower the refractive index relative to pure undopedSiO₂. An updopant may be present in a region of an optical fiber havinga negative relative refractive index when accompanied by one or moreother dopants which are not updopants. Likewise, one or more otherdopants which are not updopants may be present in a region of an opticalfiber having a positive relative refractive index. A downdopant may bepresent in a region of an optical fiber having a positive relativerefractive index when accompanied by one or more other dopants which arenot downdopants. Likewise, one or more other dopants which are notdowndopants may be present in a region of an optical fiber having anegative relative refractive index.

“Chromatic dispersion”, herein referred to as “dispersion” unlessotherwise noted, of a waveguide fiber is the sum of the materialdispersion, the waveguide dispersion, and the inter-modal dispersion. Inthe case of single mode waveguide fibers the inter-modal dispersion iszero. Zero dispersion wavelength is a wavelength at which the dispersionhas a value of zero. Dispersion slope is the rate of change ofdispersion with respect to wavelength.

“Effective area” is defined as:A _(eff)=2π(∫f ² r dr)²/(∫f ⁴ r dr),where the integration limits are 0 to ∞, and f is the transversecomponent of the electric field associated with light propagated in thewaveguide. As used herein, “effective area” or “A_(eff)” refers tooptical effective area at a wavelength of 1550 nm unless otherwisenoted.

The term “α-profile” refers to a relative refractive index profile,expressed in terms of Δ(r) which is in units of “%”, where r is radius,which follows the equation,Δ(r)=Δ(r _(o))(1−[|r−r _(o)|/(r ₁ −r _(o))]^(α),)where r_(o) is the point at which Δ(r) is maximum, r₁ is the point atwhich Δ(r) % is zero, and r is in the range r_(i)≦r≦r_(f), where Δ isdefined above, r_(i) is the initial point of the α-profile, r_(f) is thefinal point of the α-profile, and α is an exponent which is a realnumber.

The mode field diameter (MFD) is measured using the Peterman II methodwherein, 2w=MFD, and w=(2∫f² r dr/∫[df/dr]² r dr), the integral limitsbeing 0 to ∞.

The bend resistance of a waveguide fiber can be gauged by inducedattenuation under prescribed test conditions.

One type of bend test is the lateral load microbend test. In thisso-called “lateral load” test, a prescribed length of waveguide fiber isplaced between two flat plates. A #70 wire mesh is attached to one ofthe plates. A known length of waveguide fiber is sandwiched between theplates and a reference attenuation is measured while the plates arepressed together with a force of 30 newtons. A 70 newton force is thenapplied tot he plates and the increase in attenuation in dB/m ismeasured. The increase in attenuation is the lateral load attenuation ofthe waveguide.

The “pin array” bend test is used to compare relative resistance ofwaveguide fiber to bending. To perform this test, attenuation loss ismeasured for a waveguide fiber with essentially no induced bending loss.The waveguide fiber is then woven about the pin array and attenuationagain measured. The loss induced by bending is the difference betweenthe two measured attenuations. The pin array is a set of ten cylindricalpins arranged in a single row and held in a fixed vertical position on aflat surface. The pin spacing is 5 mm, center to center. The pindiameter is 0.67 mm. During testing, sufficient tension is applied tomake the waveguide fiber conform to a portion of the pin surface.

The theoretical fiber cutoff wavelength, or “theoretical fiber cutoff”,or “theoretical cutoff”, for a given mode, is the wavelength above whichguided light cannot propagate in that mode. A mathematical definitioncan be found in Single Mode Fiber Optics, Jeunhomme, pp. 39-44, MarcelDekker, New York, 1990 wherein the theoretical fiber cutoff is describedas the wavelength at which the mode propagation constant becomes equalto the plane wave propagation constant in the outer cladding. Thistheoretical wavelength is appropriate for an infinitely long, perfectlystraight fiber that has no diameter variations.

The effective fiber cutoff is lower than the theoretical cutoff due tolosses that are induced by bending and/or mechanical pressure. In thiscontext, the cutoff refers to the higher of the LP11 and LP02 modes.LP11 and LP02 are generally not distinguished in measurements, but bothare evident as steps in the spectral measurement, i.e. no power isobserved in the mode at wavelengths longer than the measured cutoff. Theactual fiber cutoff can be measured by the standard 2 m fiber cutofftest, FOTP-80 (EIA-TIA-455-80), to yield the “fiber cutoff wavelength”,also known as the “2 m fiber cutoff” or “measured cutoff”. The FOTP-80standard test is performed to either strip out the higher order modesusing a controlled amount of bending, or to normalize the spectralresponse of the fiber to that of a multimode fiber.

The cabled cutoff wavelength, or “cabled cutoff” is even lower than themeasured fiber cutoff due to higher levels of bending and mechanicalpressure in the cable environment. The actual cabled condition can beapproximated by the cabled cutoff test described in the EIA-445 FiberOptic Test Procedures, which are part of the EIA-TIA Fiber OpticsStandards, that is, the Electronics Industry Alliance—TelecommunicationsIndustry Association Fiber Optics Standards, more commonly known asFOTP's. Cabled cutoff measurement is described in EIA-455-170 CableCutoff Wavelength of Single-mode Fiber by Transmitted Power, or“FOTP-170”.

Unless otherwise noted herein, optical properties (such as dispersion,dispersion slope, etc.) are reported for the LP01 mode.

A waveguide fiber telecommunications link, or simply a link, is made upof a transmitter of light signals, a receiver of light signals, and alength of waveguide fiber or fibers having respective ends opticallyconnected to the transmitter and receiver to propagate light signalstherebetween. The length of waveguide fiber can be made up of aplurality of shorter lengths that are spliced or connected together inend to end series arrangement. A link can include additional opticalcomponents such as optical amplifiers, optical attenuators, opticalisolators, optical switches, optical filters, or multiplexing ordemultiplexing devices. One may denote a group of inter-connected linksas a telecommunications system.

A span of optical fiber as used herein includes a length of opticalfiber, or a plurality of optical fibers fused together serially,extending between optical devices, for example between two opticalamplifiers, or between a multiplexing device and an optical amplifier. Aspan may comprise one or more sections of optical fiber as disclosedherein, and may further comprise one or more sections of other opticalfiber, for example as selected to achieve a desired system performanceor parameter such as residual dispersion at the end of a span.

Various wavelength bands, or operating wavelength ranges, or wavelengthwindows, can be defined as follows: “1310 nm band” is 1260 to 1360 nm;“E-band” is 1360 to 1460 nm; “S-band” is 1460 to 1530 nm; “C-band” is1530 to 1565 nm; “L-band” is 1565 to 1625 nm; and “U-band” is 1625 to1675 nm.

The optical fiber disclosed herein comprises a core and a cladding layer(or cladding) surrounding and directly adjacent the core. The claddinghas a refractive index profile, Δ_(CLAD)(r). Preferably, Δ_(CLAD)(r)=0throughout the cladding. The core comprises a refractive index profile,Δ_(CORE)(r). In preferred embodiments, the core is comprised of aplurality of core portions, each having respective refractive indexprofiles, for example Δ_(CORE1)(r), Δ_(CORE2)(r), and so on.

Preferably, the core is comprised of silica doped with germanium, i.e.germania doped silica. Dopants other than germanium, singly or incombination, may be employed within the core, and particularly at ornear the centerline, of the optical fiber disclosed herein to obtain thedesired refractive index and density. In preferred embodiments, the coreof the optical fiber disclosed herein has a non-negative refractiveindex profile, more preferably a positive refractive index profile,wherein the core is surrounded by and directly adjacent to a claddinglayer.

Preferably, the refractive index profile of the optical fiber disclosedherein is non-negative from the centerline to the outer radius of thecore, r_(CORE). In preferred embodiments, the optical fiber contains noindex-decreasing dopants in the core.

Optical waveguide fibers 100 are disclosed herein which preferablycomprise: a central region extending radially outwardly from thecenterline to a central region outer radius, R₁, and having a relativerefractive index percent, Δ₁ % (r) with a maximum relative refractiveindex percent, Δ_(1MAX); a first annular region (or moat) 30 surroundingthe central region 20 and directly adjacent thereto, extending radiallyoutwardly to a first annular region outer radius, R₂, having a width W₂disposed at a midpoint R_(2MID), and having a non-negative relativerefractive index percent, Δ₂ % (r) with a minimum relative refractiveindex percent, Δ_(2MIN), where Δ₂ % (r)≧0 ; a second annular region (orring) 50 surrounding the first annular region 30 and preferably directlyadjacent thereto, having a width W₃ disposed at a midpoint R_(3MID), andhaving a positive relative refractive index percent, Δ₃ % (r)>0, with amaximum relative refractive index percent, Δ_(3,MAX), wherein preferablyΔ_(1MAX)>Δ_(3MAX)>Δ_(2MIN)>0; and an outer annular cladding region 200surrounding the second annular region 50 and preferably adjacent theretoand having a relative refractive index percent, Δ_(c) % (r). The firstannular region also has a maximum relative refractive index, Δ_(2,MAX),wherein Δ_(1MAX)>Δ_(3MAX)>Δ_(2MAX) and preferably Δ_(2MAX)>0. The coreends and the cladding begins at a radius r_(CORE).

In some preferred embodiments, the core may comprise a relativerefractive index profile having a so-called centerline dip which mayoccur as a result of one or more optical fiber manufacturing techniques.However, the centerline dip in any of the refractive index profilesdisclosed herein is optional.

The first annular region 30 extends from the R₁ to the outer radius R₂.The width W₂ is defined as the radial distance between R₁ and R₂. Themidpoint R_(2MID) occurs in the middle of R₁ and R₂. Preferably, thefirst annular region 30 is adjacent the central core region 20.

The ring 50 extends from R₂ to the ring outer radius R₃. The ring widthW₃ is defined as the radial distance between R₂ and R₃. The ring 50 hasa positive relative refractive index profile with a “peak” or a maximumrelative refractive index percent, A_(3,MAX). R_(3HHi) marks the firstradially inward, or centermost, occurrence of the half-height ofA_(3,MAX). R_(3HHj) marks the first radially outward occurrence of thehalf-height of Δ_(3,MAX). The ring half-height peak width HHPW₃ isbounded by inner and outer radii, R_(3HHi) and R_(3HHj), respectively.The midpoint of the ring half-height peak width HHPW₃ occurs at a radiusR_(3HHmid) which is half the radial distance between R_(3HHi) andR_(3HHj) Preferably, Δ_(3,MAX) occurs at R_(3HHMID). Preferably,R_(3HHMID) coincides with the middle of the ring 50, R_(3MID), betweenR₂ and R₃. Preferably, the second annular region 50 is adjacent thefirst annular region 30.

1_(st) Set of Preferred Embodiments

Tables 1-4 list an illustrative first set of preferred embodiments,Examples 1-10. FIGS. 1-10 show the corresponding refractive indexprofiles of Examples 1-10 in curves 1-10, respectively. TABLE 1 Example1 2 3 4 5 Δ_(1MAX) % 0.705 0.705 1.06 0.79 0.67 Δ_(AMAX) % 0.705 0.7051.06 0.79 0.67 Δ_(BMAX) % 0.44 0.44 0.40 0.41 0.52 |Δ_(AMAX) − Δ_(BMAX)|μm 0.265 0.265 0.66 0.38 0.15 Δ_(1MAX) − Δ_(BMAX) μm 0.265 0.265 0.660.38 0.15 R₁ μm 4 4 3.6 3.6 4.3 R_(1QH) μm 3.45 3.45 3.2 3.5 3.6 α_(1A)4.5 4.5 4.3 8.1 6.7 α_(1B) 3.1 3.1 8.0 8.0 1.7 Δ_(2,MIN) % 0.0 0.0 0.00.01 0.01 R₂ μm 8.4 8.4 8.6 8.5 8.3 W₂ μm 4.4 4.4 5 4.9 4 R_(2MID) μm6.4 6.4 6.1 6.1 6.3 Δ_(3MAX) % 0.095 0.095 0.09 0.09 0.09 R_(3HHi) μm8.7 8.7 8.5 8.7 8.6 R_(3HHJ) μm 12.3 12.3 12.3 12.2 12.1 HHPW3 μm 3.63.6 3.8 3.5 3.5 R_(3HHMID) μm 10.5 10.5 10.4 10.5 10.4 R₃ = R_(CORE) μm12.6 12.6 12.6 12.5 12.4 W₃ μm 4.2 4.2 4 4 4.1 R_(3MID) μm 10.5 10.510.6 10.5 10.4

TABLE 2 Example 1 2 3 4 5 Dispersion @ 1285 nm ps/nm-km −9.5 −9.1 −9.1−8.9 −9.8 Dispersion @ 1310 nm ps/nm-km −7.4 −7.0 −7.0 −6.9 −7.6Dispersion @ 1330 nm ps/nm-km −5.8 −5.4 −5.4 −5.4 −6.0 Dispersion @ 1440nm ps/nm-km 1.9 2.1 2.0 2.0 1.9 Dispersion @ 1530 nm ps/nm-km 7.0 7.37.1 7.1 7.3 Dispersion @ 1550 nm ps/nm-km 8.1 8.4 8.2 8.1 8.5 Dispersion@ 1565 nm ps/nm-km 8.9 9.2 9.0 8.9 9.3 Dispersion @ 1625 nm ps/nm-km12.1 12.3 12.0 12.0 12.6 Slope @ 1550 nm ps/nm²-km 0.054 0.053 0.0520.052 0.056 Lambda Zero nm 1398 1393 1394 1395 1399 MFD @ 1550 nm um9.24 9.32 9.11 9.21 9.18 Aeff @ 1550 nm um² 63.1 64.3 61.6 62.9 62.0 PinArray @ 1550 nm dB 12.2 13.6 11.0 11.6 7.1 Lateral Load @ 1550 nm dB/m1.6 1.7 1.2 1.4 0.9 Attenuation @ 1550 nm dB/km 0.193 0.194 0.195 0.1950.192 LP11 nm 1657 1655 1600 1650 1658 Cable Cutoff nm 1219 1217 11621212 1220

TABLE 3 Example 6 7 8 9 10 Δ_(1MAX) % 0.702 0.705 0.78 0.702 0.702Δ_(AMAX) % 0.702 0.705 0.78 0.702 0.702 Δ_(BMAX) % 0.49 0.44 0.44 0.500.50 |Δ_(AMAX) − Δ_(BMAX|) μm 0.21 0.27 0.38 0.20 0.20 Δ_(1MAX) −Δ_(BMAX) μm 0.21 0.265 0.34 0.20 0.20 R₁ μm 4 4 3.8 3.9 3.9 R_(1QH) μm3.4 3.5 3.3 3.4 3.4 α_(1A) 4.4 4.5 4.5 4.5 α_(1B) 3.1 3.1 3.0 3.1 3.1Δ_(2,MIN) % 0.025 0.025 0.025 0.025 0.025 R₂ μm 8.2 9.9 7.8 9.1 8.7 W₂μm 4.2 5.9 4 5.2 4.8 R_(2MID) μm 6.1 7 5.8 6.5 6.3 Δ_(3MAX) % 0.095 0.230.105 0.106 0.106 R_(3HHi) μm 8.7 10.2 8.6 9.6 9.2 R_(3HHJ) μm 12.6 11.912.5 13.7 13.1 HHPW3 μm 3.9 1.7 3.9 4.1 3.9 R_(3HHMID) μm 10.7 11 10.611.7 11.2 R₃ = R_(CORE) μm 13 12.1 13.9 14.0 13.5 W₃ μm 4.8 6.2 6.1 4.94.8 R_(3MID) μm 10.6 11 10.9 11.6 11.1

TABLE 4 Example 6 7 8 9 10 Dispersion @ 1285 nm ps/nm-km −9.8 −9.7 −9.8−9.7 −9.7 Dispersion @ 1310 nm ps/nm-km −7.7 −7.6 −7.7 −7.5 −7.6Dispersion @ 1330 nm ps/nm-km −6.1 −6.0 −6.1 −5.9 −6.0 Dispersion @ 1440nm ps/nm-km 1.6 1.7 1.6 1.7 1.6 Dispersion @ 1530 nm ps/nm-km 7.0 7.06.9 6.9 6.9 Dispersion @ 1550 nm ps/nm-km 8.1 8.1 8.1 8.0 8.0 Dispersion@ 1565 nm ps/nm-km 8.9 9.0 8.9 8.8 8.8 Dispersion @ 1625 nm ps/nm-km12.2 12.2 12.2 11.9 11.9 Slope @ 1550 nm ps/nm²-km 0.056 0.055 0.0560.054 0.054 Lambda Zero nm 1405 1403 1406 1400 1404 MFD @ 1550 nm um9.25 9.51 9.33 9.22 9.24 Aeff @ 1550 nm um² 63.1 66.8 64.3 62.7 63.0 PinArray @ 1550 nm dB 6.7 9.2 7.2 7.1 7.0 Lateral Load @ 1550 nm dB/m 1.43.0 1.7 2.5 2.0 Attenuation @ 1550 nm dB/km 0.193 0.192 0.193 0.1930.193 LP11 nm 1821 1974 1865 2026 1950 Cable Cutoff nm 1072 1225 10151176 1100 Fiber Cutoff nm 1322 1475 1264 1426 1350

A preferred embodiment in the first set of preferred embodimentsillustrated in FIG. 8, represented by the refractive index profile ofExample 8 in curve 8, was fabricated using an OVD method. Example 8exhibited optical characteristics similar to Example 6.

Referring to FIGS. 1-10, an optical waveguide fiber 100 disclosed hereinpreferably comprises: a central region extending radially outwardly fromthe centerline to a central region outer radius, R₁, and having arelative refractive index percent, Δ₁ % (r) with a maximum relativerefractive index percent, Δ_(1MAX), the central region comprising afirst portion, or centermost portion, the first portion extendingradially outwardly from the centerline to a radius, R_(A), and having amaximum relative refractive index percent, Δ_(AMAX), whereinΔ_(AMAX)=Δ_(1MAX), i.e. Δ_(MAX) occurs in the first portion, the centralregion further comprising a second portion surrounding and preferablydirectly adjacent to the first portion, the second portion extendingfrom R_(A) to R₁ and having a maximum relative refractive index percent,Δ_(BMAX), wherein Δ_(MAX)>Δ_(BMAX); a first annular region (or moat) 30surrounding the central region 20 and directly adjacent thereto,extending radially outwardly to a first annular region outer radius, R₂,having a width W₂ disposed at a midpoint R_(2MID), and having anon-negative relative refractive index percent, Δ₂ % (r) with a minimumrelative refractive index percent, Δ_(2MIN), where Δ₂ % (r)≧0; a secondannular region (or ring) 50 surrounding the first annular region 30 andpreferably directly adjacent thereto, having a width W₃ disposed at amidpoint R_(3MID), and having a positive relative refractive indexpercent, Δ₃ % (r)>0, with a maximum relative refractive index percent,A_(3,MAX), wherein preferably Δ_(1MAX)>Δ_(3MAX)>Δ_(2MIN)≧0, morepreferably Δ_(1MAX)>Δ_(3MAX)>Δ_(2MIN)>0; and an outer annular claddingregion 200 surrounding the second annular region 50 and preferablyadjacent thereto and having a relative refractive index percent, Δ_(c) %(r). The core ends and the cladding begins at a radius r_(CORE).

The end of central core region 20, R₁, is preferably the beginning offirst annular core region and is defined herein to start at a radiuswhere a straight line approximation, indicated by line 21 which passestangentially through the quarter-peak height of the central region 20 isextrapolated to intersect with the Δ %=0 axis at R_(1QH).

Thus, the optical fiber 100 preferably comprises three core segments:center core region 20, first annular core region 30, and second annularcore region 50. Preferably Δ_(1,A) % (r) for some, preferably most, ofthe first portion between the centerline (r=0) and R_(A) has anα-profile with an α_(1A), greater than 2, more preferably greater than3, even more preferably greater than 4, and in some preferredembodiments greater than 5. In preferred embodiments, α_(1A) is alsoless than 10. In preferred embodiments, the central core region 20includes at least a first portion having a step-index relativerefractive index profile Δ_(1,A) % (r). The central core region 20 mayalso comprise a second portion adjacent and surrounding the firstportion having Δ_(1,B) % (r). Preferably, the maximum Δ_(1,B) % (r)(i.e. Δ_(BMAX)) is lower than the minimum Δ_(1,A) % (r) (i.e. Δ_(MAX)).Preferably, the absolute magnitude of the difference between Δ_(AMAX)and Δ_(BMAX), i.e. |Δ_(AMAX)−Δ_(BMAX)|, is greater than 0.1, morepreferably greater than 0.2, even more preferably greater than 0.3,still more preferably between 0.3 and 0.7 (in %). In preferredembodiments, the relative refractive index Δ_(1,B) % (r) has anα-profile with an α_(1B), which for some, and preferably most, of thesecond portion between r=R_(A) and r=R_(B) is preferably between 1 and10, more preferably between 2 and 9, even more preferably between 2 and5, and still more preferably between 2 and 4. Preferably, Δ_(1,B) % (r)for r<R₁ is greater than Δ₂ % (r) for R1<r<R2.

Preferably, Δ % (r) is greater than or equal to 0% for radii up to 15microns, more preferably up to 30 microns, and even more preferably forall radii, i.e. from r=0 at the centerline to r=R,max, where R,max isthe outermost radius of the silica-based part of the optical fiber(excluding any coating).

Central region 20 comprises a maximum relative refractive index or peakΔ₁ %, Δ_(1MAX), between 0.6 and 1.2%, more preferably between 0.7 and1.1%, even more preferably between 0.7 and 0.8%, and a radius R1 ofbetween about 2 and 6 microns, more preferably between about 3 and 5microns, as defined by a straight line approximation wherein a straightline passes tangentially through the quarter-peak height of the centralregion 20 and is extrapolated to intersect with the Δ %=0 axis atR_(1QH). The first portion of the central region 20 ends at a radius of1 μm. Preferably, the quarter-peak height occurs at a radius betweenabout 2 μm and about 4 μm. Preferably, Δ_(BMAX) is between 0.3 and 0.5%.Preferably, the difference between Δ_(AMAX) and Δ_(BMAX) is between 0.2and 0.7%, more preferably between 0.2 and 0.5%. Preferably, thedifference between Δ_(1MAX) and Δ_(BMAX) is greater than 0.1% morepreferably between 0.1% and 0.7%, and in some preferred embodiments isbetween 0.15% and 0.4%.

The first annular core region 30 comprises a minimum relative refractiveindex or minimum Δ₂ %, Δ2,MIN, greater than or equal to 0 and less than0.1%, more preferably greater than or equal to 0 and less than 0.05%,and begins at a radius of between about 2 microns and about 6 microns,more preferably at a radius of between about 3 microns and about 5microns, and most preferably at R₁. The first annular core region 30 mayhave a maximum Δ₂ %, Δ2,MAX, wherein Δ_(2,MAX)>Δ_(2,MIN). Preferably,the moat has a width W₂ of between 3 and 7 μm, more preferably between 4and 6 μm. Preferably, the moat has a midpoint R_(2MID) between 5 and 8μm, more preferably between 6 and 7 μm.

The end of the first annular core region 30 and the beginning of secondannular core region 50 is defined herein to occur at a radius where astraight line approximation passes tangentially through the half-peakheight (at R_(3HHi)) of the centermost side of second annular coreregion 50 and is extrapolated to intersect with the Δ %=0 axis. Firstannular core region 30 ends and second annular core region 50 beginsbetween about 7 microns and about 10 microns, more preferably betweenabout 7 microns and about 9 microns. Second annular core region 50 has amaximum relative refractive index or peak Δ₃ %, Δ_(3,MAX), of betweenabout 0.05% and 0.15%. The outer annular cladding region or claddingsegment 200 is disposed adjacent and surrounding second annular coresegment 50, and preferably begins from a radius of between about 11microns and about 18 microns, more preferably between about 12 micronsand about 16 microns. Δ_(1,MAX) is greater than Δ_(3,MAX)·Δ_(3,MAX) isgreater than Δ_(2,MIN), and preferably Δ_(3,MAX) is greater than Δ₂(r)at any radius in the first annular region. Thus,Δ_(1,MAX)>Δ_(3,MAX)>Δ_(2,MIN)≧0. Δ_(2,MAX) is preferably less than 0.5Δ_(3,MAX), more preferably less than 0.4 ×_(3,MAX). Δ_(3,MAX) ispreferably less than 0.5 Δ_(1,MAX), more preferably less than 0.4Δ_(1,MAX), and in some preferred embodiments less than 0.3 Δ_(1,MAX).Preferably, the ring has a width W₃ of between 1 and 6 μm, morepreferably between 1 and 5 μm, even more preferably between 2 and 4 μm.Preferably, the ring has a midpoint R_(3MiD) between 10 and 12 μm.Preferably the half-height peak width of the ring HHPW3 is between 1 and4 μm, and the half height midpoint of the ring R_(3HHMID) is between 10and 12 μm.

2^(nd) Set of Preferred Embodiments

FIG. 11 shows relative refractive index profiles of Examples 11 & 12,labeled curve 11 & 12, respectively, which are illustrative of a secondset of preferred embodiments. Tables 5 and 6 list characteristics ofExamples 11-12. TABLE 5 Example 11 12 Δ_(1MAX) % 0.54 0.46 Δ_(AMAX) %0.54 0.46 Δ_(BMAX) % 0.54 0.46 |Δ_(AMAX) − Δ_(BMAX)| μm 0 0 Δ_(1MAX) −Δ_(BMAX) μm 0 0 R₁ μm 4.0 3.6 R_(1QH) μm 3.5 3.3 α_(1B) 1.6 9.1Δ_(2,MIN) % 0.02 0.01 R₂ μm 6.6 7.4 W₂ μm 2.6 3.8 R_(2MID) μm 5.3 5.5Δ_(3MAX) % 0.07 0.10 R_(3HHi) μm 6.9 7.5 R_(3HHJ) μm 12.6 11.55 HHPW3 μm5.7 4.0 R_(3HHMID) μm 9.8 9.5 R₃ = R_(CORE) μm 12.8 11.7 W₃ μm 10.2 4.3R_(3MID) μm 7.7 9.6

TABLE 6 Example 11 12 Dispersion @ 1285 nm ps/nm-km −9.1 −8.5 Dispersion@ 1310 nm ps/nm-km −7.0 −6.5 Dispersion @ 1330 nm ps/nm-km −5.5 −5.1Dispersion @ 1440 nm ps/nm-km 2.0 2.0 Dispersion @ 1530 nm ps/nm-km 7.37.0 Dispersion @ 1550 nm ps/nm-km 8.4 8.1 Dispersion @ 1565 nm ps/nm-km9.3 8.9 Dispersion @ 1625 nm ps/nm-km 12.5 12.1 Slope @ 1550 nmps/nm²-km 0.055 0.054 Lambda Zero nm 1397 1399 MFD @ 1550 nm um 9.029.33 Aeff @ 1550 nm um² 60.1 65.1 Pin Array @ 1550 nm dB 3.7 9.0 LateralLoad @ 1550 nm dB/m 0.5 1.4 Attenuation @ 1550 nm dB/km 0.195 0.198 LP11nm 1698 1699 Cable Cutoff nm 1260 1261

Referring to FIG. 11 and applying the nomenclature of FIG. 1, an opticalwaveguide fiber 100 disclosed herein preferably comprises: a centralregion extending radially outwardly from the centerline to a centralregion outer radius, R₁, and having a relative refractive index percent,Δ₁ % (r) with a maximum relative refractive index percent, Δ_(1MAX), thecentral region comprising a first portion, or centermost portion, thefirst portion extending radially outwardly from the centerline to aradius, R_(A), and having a maximum relative refractive index percent,Δ_(AMAX), wherein Δ_(AMAX)=Δ_(1MAX), i.e. Δ_(1MAX) occurs in the firstportion, the central region further comprising a second portionsurrounding and preferably directly adjacent to the first portion, thesecond portion extending from R_(A) to R₁ and having a maximum relativerefractive index percent, Δ_(BMAX), wherein Δ_(AMAX) is substantiallyequal to Δ_(BMAX); a first annular region (or moat) 30 surrounding thecentral region 20 and directly adjacent thereto, extending radiallyoutwardly to a first annular region outer radius, R₂, having a width W₂disposed at a midpoint R_(2MID), and having a non-negative relativerefractive index percent, Δ₂ % (r) with a minimum relative refractiveindex percent, Δ_(2MIN), where Δ₂ % (r)>0; a second annular region (orring) 50 surrounding the first annular region 30 and preferably directlyadjacent thereto, having a width W₃ disposed at a midpoint R_(3MID), andhaving a positive relative refractive index percent, Δ₃ % (r)>0, with amaximum relative refractive index percent, Δ_(3,MAX), wherein preferablyΔ_(1MAX)>Δ_(3MAX)>Δ_(2MIN)>0, more preferablyΔ_(1MAX)>Δ_(3MAX)>Δ_(2MIN)>0; and an outer annular cladding region 200surrounding the second annular region 50 and preferably adjacent theretoand having a relative refractive index percent, Δ_(c) % (r). The coreends and the cladding begins at a radius r_(CORE).

The end of central core region 20, R₁, is preferably the beginning offirst annular core region and is defined herein to start at a radiuswhere a straight line approximation which passes tangentially throughthe quarter-peak height of the central region 20 is extrapolated tointersect with the Δ %=0 axis at R_(1QH).

Thus, the optical fiber 100 preferably comprises three core segments:center core region 20, first annular core region 30, and second annularcore region 50. In preferred embodiments, the central core region 20includes at least a first portion having a substantially constantrelative refractive index profile Δ_(1,A) % (r). The central core region20 may also comprise a second portion adjacent and surrounding the firstportion having Δ_(1,B) % (r). Preferably, the maximum Δ_(1,B) % (r)(i.e. Δ_(BMAX)) is substantially equal to the maximum Δ_(1,A) % (r)(i.e. Δ_(AMAX)), wherein the absolute magnitude of the differencebetween Δ_(AMAX) and Δ_(BMAX), ie. |Δ_(AMAX)−Δ_(BMAX)|, is preferablyless than 0.1, and in some preferred embodiments is less than 0.05 (in%). In preferred embodiments, the relative refractive index Δ_(1,B) %(r) has an α-profile with an α_(1B), which is preferably between 1 and10 for some, preferably most, of the second portion between r=R_(A) andr=R_(B). Preferably, Δ_(1,B) % (r) for r<R₁ is greater than Δ₂ % (r) forR1<r<R2.

Preferably, Δ % (r) is greater than or equal to 0% for radii up to 15microns, more preferably up to 30 microns, and even more preferably forall radii, i.e. from r=0 at the centerline to r=R,max, where R,max isthe outermost radius of the silica-based part of the optical fiber(excluding any coating).

Central region 20 comprises a maximum relative refractive index or peakΔ₁ %, Δ_(1,MAX), between 0.3 and 0.8%, more preferably between 0.4 and0.7%, even more preferably between 0.4 and 0.6%, and a radius R1 ofbetween about 2 and 6 microns, more preferably between about 3 and 5microns, as defined by a straight line approximation wherein a straightline passes tangentially through the quarter-peak height of the centralregion 20 and is extrapolated to intersect with the Δ %=0 axis atR_(1QH). The first portion of the central region 20 ends at a radius of1 μm. Preferably, the quarter-peak height occurs at a radius betweenabout 2 μm and about 4 μm. Preferably, Δ_(BMAX) is between 0.3 and 0.5%.Preferably, the difference between Δ_(AMAX) and Δ_(BMAX) is less than0.1%, more preferably less than 0.05%.

The first annular core region 30 comprises a minimum relative refractiveindex or minimum Δ₂ %, Δ_(2,MIN), greater than or equal to 0 and lessthan 0.1%, more preferably greater than or equal to 0 and less than0.05%, and begins at a radius of between about 2 microns and about 6microns, more preferably at a radius of between about 3 microns andabout 5 microns, and most preferably at R₁. The first annular coreregion 30 may have a maximum Δ₂ %, Δ_(2,MAX), whereinΔ_(2,MAX)≧Δ_(2,MIN). Preferably, the moat has a width W₂ of between 1and 5 μm, more preferably between 2 and 4 μm. Preferably, the moat has amidpoint R_(2MID) between 4 and 7 μm, more preferably between 5 and 6μm.

The end of the first annular core region 30 and the beginning of secondannular core region 50 is defined herein to occur at a radius where astraight line approximation passes tangentially through the half-peakheight (at R_(3HHi)) of the centermost side of second annular coreregion 50 and is extrapolated to intersect with the Δ %=0 axis. Firstannular core region 30 ends and second annular core region 50 beginsbetween about 5 microns and about 9 microns, more preferably betweenabout 6 microns and about 8 microns. Second annular core region 50 has amaximum relative refractive index or peak Δ₃ % , Δ_(3,MAX), of betweenabout 0.05% and 0.2%, preferably between about 0.05% and 1.5%. The outerannular cladding region or cladding segment 200 is disposed adjacent andsurrounding second annular core segment 50, and preferably begins from aradius of between about 10 microns and about 18 microns, more preferablybetween about 11 microns and about 16 microns. Δ_(1,MAX) is greater thanΔ_(3,MAX). Δ_(3,MAX) is greater than Δ_(2,MIN), and preferably Δ_(3,MAX)is greater than Δ₂(r) at any radius in the first annular region. Thus,Δ_(1,MAX)>Δ_(3,MAX)>Δ_(2,MIN)≧0. Δ_(2,MAX) is preferably less than 0.5Δ_(3,MAX), more preferably less than 0.4 Δ_(3,MAX). Δ_(3,MAX) ispreferably less than 0.5 Δ_(1,MAX), more preferably less than 0.4Δ_(1,MAX), and in some preferred embodiments less than 0.3 Δ_(1,MAX).Preferably, the ring has a width W₃ of between 3 and 12 μm, morepreferably between 4 and 11 μm. Preferably, the ring has a midpointR_(3MiD) between 7 and 10 μm. Preferably the half-height peak width ofthe ring HHPW3 is between 3 and 6 μm and the half-height midpoint of thering R_(3HMID) is between 9 and 10 μm.

3^(rd) Set of Preferred Embodiments

FIG. 12 shows relative refractive index profiles of Examples 13 & 14,labeled curve 13 & 14, respectively, which are illustrative of a thirdset of preferred embodiments. Tables 7 and 8 list characteristics ofExamples 13-14. TABLE 7 Example 13 14 Δ_(1MAX) % 0.60 0.63 Δ_(AMAX) %0.60 0.63 Δ_(BMAX) % 0.58 0.54 |Δ_(AMAX) − Δ_(BMAX)| μm 0.02 0.09Δ_(1MAX) − Δ_(BMAX) μm 0.02 0.09 R₁ μm 4.3 4.6 R_(1QH) μm 3.4 3.5 α_(1B)0.94 0.95 Δ_(2,MIN) % 0.002 0.003 R₂ μm 10.6 11.1 W₂ μm 6.3 6.5 R_(2MID)μm 7.5 7.9 Δ_(3MAX) % 0.46 0.24 R_(3HHi) μm 10.8 11.2 R_(3HHJ) μm 11.3512.5 HHPW3 μm 0.6 1.3 R_(3HHMID) μm 11.1 11.9 R₃ = R_(CORE) μm 11.5 12.6W₃ μm 0.9 1.5 R_(3MID) μm 11.1 11.9

TABLE 8 Example 13 14 Dispersion @ 1285 nm ps/nm-km −10.1 −10.1Dispersion @ 1310 nm ps/nm-km −8.0 −7.9 Dispersion @ 1330 nm ps/nm-km−6.4 −6.2 Dispersion @ 1440 nm ps/nm-km 1.2 1.8 Dispersion @ 1530 nmps/nm-km 6.5 7.2 Dispersion @ 1550 nm ps/nm-km 7.5 8.3 Dispersion @ 1565nm ps/nm-km 8.3 9.1 Dispersion @ 1625 nm ps/nm-km 11.4 12.3 Slope @ 1550nm ps/nm²-km 0.053 0.055 Lambda Zero nm 1409 1399 MFD @ 1550 nm um 9.049.10 Aeff @ 1550 nm um² 60.2 60.9 Pin Array @ 1550 nm dB 12.6 11.4Lateral Load @ 1550 nm dB/m 1.4 1.7 Attenuation @ 1550 nm dB/km 0.1940.192 LP11 nm 1625 1722 Cable Cutoff nm 1187 1284

Referring to FIG. 12 and applying the nomenclature of FIG. 1, an opticalwaveguide fiber 100 disclosed herein preferably comprises: a centralregion extending radially outwardly from the centerline to a centralregion outer radius, R₁, and having a relative refractive index percent,Δ₁ % (r) with a maximum relative refractive index percent, Δ_(1MAX), thecentral region comprising a first portion, or centermost portion, thefirst portion extending radially outwardly from the centerline to aradius, R_(A), and having a maximum relative refractive index percent,Δ_(AMAX), wherein Δ_(AMAX)=Δ_(1,MAX), i.e. Δ_(1MAX) occurs in the firstportion, the central region further comprising a second portionsurrounding and preferably directly adjacent to the first portion, thesecond portion extending from R_(A) to R₁ and having a maximum relativerefractive index percent, Δ_(BMAX), wherein Δ_(AMAX) is substantiallyequal to Δ_(BMAX); a first annular region (or moat) 30 surrounding thecentral region 20 and directly adjacent thereto, extending radiallyoutwardly to a first annular region outer radius, R₂, having a width W₂disposed at a midpoint R_(2MD), and having a non-negative relativerefractive index percent, Δ₂ % (r) with a minimum relative refractiveindex percent, Δ_(2MIN), where Δ₂ % (r)≧0; a second annular region (orring) 50 surrounding the first annular region 30 and preferably directlyadjacent thereto, having a width W₃ disposed at a midpoint R_(3MID), andhaving a positive relative refractive index percent, Δ₃ % (r)>0, with amaximum relative refractive index percent, Δ_(3,MAX), wherein preferablyΔ_(1MAX)>Δ_(3MAX)>Δ_(2MIN)>0, more preferablyΔ_(1MAX)>Δ_(3MAX)>Δ_(2MIN)>0; and an outer annular cladding region 200surrounding the second annular region 50 and preferably adjacent theretoand having a relative refractive index percent, Δ_(c) % (r). The coreends and the cladding begins at a radius r_(CORE).

The end of central core region 20, R₁, is preferably the beginning offirst annular core region and is defined herein to start at a radiuswhere a straight line approximation which passes tangentially throughthe quarter-peak height of the central region 20 is extrapolated tointersect with the Δ %=0 axis at R_(1QH).

Thus, the optical fiber 100 preferably comprises three core segments:center core region 20, first annular core region 30, and second annularcore region 50. In preferred embodiments, the central core region 20includes at least a first portion having a substantially constantrelative refractive index profile Δ_(1,A) % (r). The central core region20 may also comprise a second portion adjacent and surrounding the firstportion having Δ_(1,B) % (r). Preferably, the maximum Δ_(1,B) % (r)(i.e. Δ_(BMAX)) is less than or equal to the maximum Δ_(1,A) % (r) (i.e.Δ_(AMAX)). Preferably, the absolute magnitude of the difference betweenΔ_(AMAX) and Δ_(BMAX), i.e. |Δ_(AMAX)−Δ_(BMAX)|, is less than 0.2, morepreferably less than 0.1, even more preferably less than 0.05 (in %). Inpreferred embodiments, the relative refractive index Δ_(1,B) % (r) hasan α-profile with an α_(1B), which is preferably between 0.5 and 2 forsome, preferably most, of the second portion between r=R_(A) andr=R_(B), and in preferred embodiments has an α_(1B) of about 1.Preferably, Δ_(1,B) % (r) for r<R1 is greater than Δ₂ % (r) for R1<r<R2.

Preferably, Δ % (r) is greater than or equal to 0% for radii up to 15microns, more preferably up to 30 microns, and even more preferably forall radii, i.e. from r=0 at the centerline to r=R,max, where R,max isthe outermost radius of the silica-based part of the optical fiber(excluding any coating).

Central region 20 comprises a maximum relative refractive index or peakΔ₁ %, Δ_(1,MAX), between 0.4 and 0.8%, more preferably between 0.5 and0.8%, even more preferably between 0.5 and 0.7%, and a radius R1 ofbetween about 3 and 6 microns, more preferably between about 3 and 5microns, as defined by a straight line approximation wherein a straightline passes tangentially through the quarter-peak height of the centralregion 20 and is extrapolated to intersect with the Δ %=0 axis atR_(1QH). The first portion of the central region 20 ends at a radius of1 μm. Preferably, the quarter-peak height occurs at a radius betweenabout 2 μm and about 4 μm. Preferably, Δ_(BMAX) is between 0.4 and 0.7%.Preferably, the difference between Δ_(AMAX) and Δ_(BMAX) is less than0.2%, more preferably less than 0.1%.

The first annular core region 30 comprises a minimum relative refractiveindex or minimum Δ₂ %, Δ_(2,MIN), greater than or equal to 0 and lessthan 0.1%, more preferably greater than or equal to 0 and less than0.05%, and begins at a radius of between about 3 microns and about 6microns, more preferably at a radius of between about 3 microns andabout 5 microns, and most preferably at R₁. The first annular coreregion 30 may have a maximum Δ₂ %, Δ_(2,MAX), whereinΔ_(2,MAX)≧Δ_(2,MIN). Preferably, the moat has a width W₂ of between 4and 8 μm, more preferably between 5 and 7 μm. Preferably, the moat has amidpoint R_(2MID) between 6 and 9 μm, more preferably between 7 and 8μm.

The end of the first annular core region 30 and the beginning of secondannular core region 50 is defined herein to occur at a radius where astraight line approximation passes tangentially through the half-peakheight (at R_(3HHi)) of the centermost side of second annular coreregion 50 and is extrapolated to intersect with the Δ %=0 axis. Firstannular core region 30 ends and second annular core region 50 beginsbetween about 9 microns and about 12 microns, more preferably betweenabout 10 microns and about 12 microns. Second annular core region 50 hasa maximum relative refractive index or peak Δ₃ %, Δ_(3,MAX), of betweenabout 0.1% and 0.6%, preferably between about 0.2% and 0.5%. The outerannular cladding region or cladding segment 200 is disposed adjacent andsurrounding second annular core segment 50, and preferably begins from aradius of between about 10 microns and about 18 microns, more preferablybetween about 11 microns and about 16 microns. Δ_(1,MAX) is greater thanΔ_(3,MAX). Δ_(3,MAX) is greater than Δ_(2,MIN), and preferably Δ_(3,MAX)is greater than Δ₂(r) at any radius in the first annular region. Thus,Δ_(1,MAX)>Δ_(3,MAX)>Δ_(2,MIN)≧0. Δ_(2,MAX) is preferably less than 0.5Δ_(3,MAX), more preferably less than 0.4 Δ_(3,MAX). Δ_(3,MAX) ispreferably less than 0.9 Δ_(1,MAX), more preferably less than 0.8Δ_(1,MAX), and in some preferred embodiments less than 0.5 Δ_(1,MAX).Preferably, the ring has a width W₃ of between 0.5 and 3 μm, morepreferably between 1 and 2 μm. Preferably, the ring has a midpointR_(3MiD) between 10 and 12 μm. Preferably the half-height peak width ofthe ring HHPW3 is between 0.5 μm and 1.5 μm and the half-height midpointof the ring R_(3HMID) is between 11 μm and 12 μm.

4^(th) Set of Preferred Embodiments

FIG. 13 shows relative refractive index profiles of Examples 15 & 16,labeled curve 15 & 16, respectively, which are illustrative of a fourthset of preferred embodiments. Tables 9 and 10 list characteristics ofExamples 15-16. TABLE 9 Example 15 16 Δ_(1MAX) % 0.73 0.71 Δ_(AMAX) %0.21 0.19 Δ_(BMAX) % 0.73 0.71 |Δ_(AMAX) − Δ_(BMAX)| μm 0.52 0.52Δ_(1MAX) − Δ_(BMAX) μm 0.52 0.52 R₁ μm 3.4 3.6 R_(1QH) μm 3.0 3.1 α_(1B)1.2 1.1 Δ_(2,MIN) % 0.01 0.01 R₂ μm 9.4 8.9 W₂ μm 6 5.3 R_(2MID) μm 6.46.3 Δ_(3MAX) % 0.25 0.11 R_(3HHi) μm 9.5 9.0 R_(3HHJ) μm 10.65 11.8HHPW3 μm 1.2 2.8 R_(3HHMID) μm 10.1 10.4 R₃ = R_(CORE) μm 10.8 12.0 W₃μm 1.4 3.1 R_(3MID) μm 10.1 10.5

TABLE 10 Example 15 16 Dispersion @ 1285 nm ps/nm-km −9.4 −9.6Dispersion @ 1310 nm ps/nm-km −7.3 −7.5 Dispersion @ 1330 nm ps/nm-km−5.8 −5.9 Dispersion @ 1440 nm ps/nm-km 1.7 1.6 Dispersion @ 1530 nmps/nm-km 6.8 6.9 Dispersion @ 1550 nm ps/nm-km 7.6 8.0 Dispersion @ 1565nm ps/nm-km 8.7 8.8 Dispersion @ 1625 nm ps/nm-km 11.9 12.0 Slope @ 1550nm ps/nm²-km 0.054 0.054 Lambda Zero nm 1403 1404 MFD @ 1550 nm um 9.259.30 Aeff @ 1550 nm um² 66.3 66.5 Pin Array @ 1550 nm dB 11.1 12.5Lateral Load @ 1550 nm dB/m 1.4 1.6 Attenuation @ 1550 nm dB/km 0.2150.214 LP11 nm 1628 1642 Cable Cutoff nm 1190 1204

Referring to FIG. 13 and applying the nomenclature of FIG. 1, an opticalwaveguide fiber 100 disclosed herein preferably comprises: a centralregion extending radially outwardly from the centerline to a centralregion outer radius, R₁, and having a relative refractive index percent,Δ₁ % (r) with a maximum relative refractive index percent, Δ_(1MAX), thecentral region comprising a first portion, or centermost portion, thefirst portion extending radially outwardly from the centerline to aradius, R_(A), and having a maximum relative refractive index percent,Δ_(AMAX), wherein Δ_(AMAX)=Δ_(1MAX), i.e. Δ_(1MAX) occurs in the firstportion, the central region further comprising a second portionsurrounding and preferably directly adjacent to the first portion, thesecond portion extending from R_(A) to R₁ and having a maximum relativerefractive index percent, Δ_(BMAX), wherein Δ_(AMAX) is substantiallyequal to Δ_(BMAX); a first annular region (or moat) 30 surrounding thecentral region 20 and directly adjacent thereto, extending radiallyoutwardly to a first annular region outer radius, R₂, having a width W₂disposed at a midpoint R_(2MID), and having a non-negative relativerefractive index percent, Δ₂ % (r) with a minimum relative refractiveindex percent, Δ_(2MIN), where Δ₂ % (r)≧0; a second annular region (orring) 50 surrounding the first annular region 30 and preferably directlyadjacent thereto, having a width W₃ disposed at a midpoint R_(3MID), andhaving a positive relative refractive index percent, Δ₃ % (r)>0, with amaximum relative refractive index percent, Δ_(3,MAX), wherein preferablyΔ_(1MAX)>Δ_(3MAX)>Δ_(2MIN)≧0, more preferablyΔ_(1MAX)>Δ_(3MAX)>Δ_(2MIN)>0; and an outer annular cladding region 200surrounding the second annular region 50 and preferably adjacent theretoand having a relative refractive index percent, Δ_(c) % (r). The coreends and the cladding begins at a radius r_(CORE).

The end of central core region 20, R₁, is preferably the beginning offirst annular core region and is defined herein to start at a radiuswhere a straight line approximation which passes tangentially throughthe quarter-peak height of the central region 20 is extrapolated tointersect with the Δ %=axis at R_(1QH).

Thus, the optical fiber 100 preferably comprises three core segments:center core region 20, first annular core region 30, and second annularcore region 50. In preferred embodiments, the central core region 20includes at least a first portion having a substantially constantrelative refractive index profile Δ_(1,A) % (r). The central core region20 may also comprise a second portion adjacent and surrounding the firstportion having Δ_(1,B) % (r). Preferably, the maximum Δ_(1,B) % (r)(i.e. Δ_(BMAX)) is greater than the maximum Δ_(1,A) % (r) (i.e.Δ_(AMAX)). Preferably, the absolute magnitude of the difference betweenΔ_(AMAX) and Δ_(BMAX), i.e. |Δ_(AMAX)−Δ_(BMAX)|, is greater than 0.2,more preferably greater than 0.3, even more preferably greater than 0.4,still more preferably between 0.4 and 0.7 (in %). In preferredembodiments, the relative refractive index Δ_(1,B) % (r) has anα-profile with an α_(1B), which is preferably between 0.5 and 2 forsome, preferably most, of the second portion between r=R_(A) andr=R_(B), and in preferred embodiments has an α_(1B) of about 1.Preferably, Δ_(1,B) % (r) for r<R1 is greater than Δ₂ % (r) for R1<r<R2.

Preferably, Δ % (r) is greater than or equal to 0% for radii up to 15microns, more preferably up to 30 microns, and even more preferably forall radii, i.e. from r=0 at the centerline to r=R,max, where R,max isthe outermost radius of the silica-based part of the optical fiber(excluding any coating).

Central region 20 comprises a maximum relative refractive index or peakΔ₁ %, Δ_(1,MAX), between 0.5 and 0.9%, more preferably between 0.5 and0.8%, even more preferably between 0.6 and 0.8%, and a radius R1 ofbetween about 3 and 6 microns, more preferably between about 3 and 5microns, as defined by a straight line approximation wherein a straightline passes tangentially through the quarter-peak height of the centralregion 20 and is extrapolated to intersect with the Δ %=0 axis atR_(1QH). The first portion of the central region 20 ends at a radius of1 μm. Preferably, the quarter-peak height occurs at a radius betweenabout 2 μm and about 4 μm. Preferably, Δ_(BMAX) is between 0.4 and 0.7%.Preferably, the difference between Δ_(AMAX) and Δ_(BMAX) is greater than0.4%, more preferably greater than 0.5%. Preferably, the differencebetween Δ_(1MAX) and Δ_(AMAX) is greater than 0.4%, more preferably>0.5%.

The first annular core region 30 comprises a minimum relative refractiveindex or minimum Δ₂ %, Δ_(2,MIN), greater than or equal to 0 and lessthan 0.1%, more preferably greater than or equal to 0 and less than0.05%, and begins at a radius of between aboiit 3 microns and about 6microns, more preferably at a radius of between about 3 microns andabout 5 microns, and most preferably at R₁. The first annular coreregion 30 may have a maximum Δ₂ %, Δ_(2,MAX), whereinΔ_(2,MAX)≧Δ_(2,MIN). Preferably, the moat has a width W₂ of between 4and 7 μm, more preferably between 5 and 6 μm. Preferably, the moat has amidpoint R_(2MID) between 4 and 8 μm, more preferably between 5 and 7μm.

The end of the first annular core region 30 and the beginning of secondannular core region 50 is defined herein to occur at a radius where astraight line approximation passes tangentially through the half-peakheight (at R_(3HHi)) of the centermost side of second annular coreregion 50 and is extrapolated to intersect with the Δ %=0 axis. Firstannular core region 30 ends and second annular core region 50 beginsbetween about 7 microns and about 11 microns, more preferably betweenabout 8 microns and about 10 microns. Second annular core region 50 hasa maximum relative refractive index or peak Δ₃ %, Δ_(3,MAX), of betweenabout 0.05% and 0.4%, preferably between about 0.05% and 0.3%. The outerannular cladding region or cladding segment 200 is disposed adjacent andsurrounding second annular core segment 50, and preferably begins from aradius of between about 10 microns and about 18 microns, more preferablybetween about 10 microns and about 16 microns. Δ_(1,MAX) is greater thanΔ_(3,MAX). Δ_(3,MAX) is greater than Δ_(2,MIN), and preferably Δ_(3,MAX)is greater than Δ₂(r) at any radius in the first annular region. Thus,Δ_(1,MAX)>Δ_(3,MAX)>Δ_(2,MIN)≧0. Δ_(2,MAX) is preferably less than 0.5Δ_(3,MAX), more preferably less than 0.4 Δ_(3,MAX). Δ_(3,MAX) ispreferably less than 0.5 Δ_(1,MAX), more preferably less than 0.4Δ_(1,MAX). Preferably, the ring has a width W₃ of between 0.5 and 5 μm,more preferably between 1 and 4 μm. Preferably, the ring has a midpointR_(3MiD) between 10 and 11 μm. Preferably the half-height peak width ofthe ring HHPW3 is between 1 μm and 3 μm and the half-height midpoint ofthe ring R_(3HHID) is between 10 μm and 11 μm.

Preferably, the optical fiber disclosed herein is capable oftransmitting optical signals in the 1260 nm to 1625 nm wavelength range.

Preferably, the fibers disclosed herein are made by a vapor depositionprocess. Even more preferably, the fibers disclosed herein are made byan outside vapor deposition (OVD) process. Thus, for example, known OVDlaydown, consolidation, and draw techniques may be advantageously usedto produce the optical waveguide fiber disclosed herein. Otherprocesses, such as modified chemical vapor deposition (MCVD) or vaporaxial deposition (VAD) or plasma chemical vapor deposition (PCVD) may beused. Thus, the refractive indices and the cross sectional profile ofthe optical waveguide fibers disclosed herein can be accomplished usingmanufacturing techniques known to those skilled in the art including,but in no way limited to, OVD, VAD and MCVD processes.

FIG. 14 is a schematic representation (not to scale) of an opticalwaveguide fiber 100 as disclosed herein having core 101 and an outerannular cladding or outer cladding layer or clad layer 200 directlyadjacent and surrounding the core 101.

Preferably, the cladding contains no germania or fluorine dopantstherein. More preferably, the cladding 200 of the optical fiberdisclosed herein is pure or substantially pure silica. The clad layer200 may be comprised of a cladding material which was deposited, forexample during a laydown process, or which was provided in the form of ajacketing, such as a tube in a rod-in-tube optical perform arrangement,or a combination of deposited material and a jacket. The clad layer 200may include one or more dopants. The clad layer 200 is surrounded by aprimary coating P and a secondary coating S. The refractive index of thecladding 200 is used to calculate the relative refractive indexpercentage as discussed elsewhere herein.

Referring to the Figures, the clad layer 200 has a refractive index ofN_(c) surrounding the core which is defined to have a Δ(r)=0%, which isused to calculate the refractive index percentage of the variousportions or regions of an optical fiber or optical fiber perform.

Preferably, the optical fiber disclosed herein has a silica-based coreand cladding. In preferred embodiments, the cladding has an outerdiameter, 2*R,max, of about 125 μm. Preferably, the outer diameter ofthe cladding has a constant diameter along the length of the opticalfiber. In preferred embodiments, the refractive index of the opticalfiber has radial symmetry. Preferably, the outer diameter of the corehas a constant diameter along the length of the optical fiber.Preferably, one or more coatings surround and are in contact with thecladding. The coating is preferably a polymer coating such as acrylate.Preferably the coating has a constant diameter, radially and along thelength of the fiber.

As shown in FIG. 15, an optical fiber 100 as disclosed herein may beimplemented in an optical fiber communication system 330. System 330includes a transmitter 334 and a receiver 336, wherein optical fiber 100allows transmission of an optical signal between transmitter 334 andreceiver 336. System 330 is preferably capable of 2-way communication,and transmitter 334 and receiver 336 are shown for illustration only.The system 330 preferably includes a link which has a section or a spanof optical fiber as disclosed herein. The system 330 may also includeone or more optical devices optically connected to one or more sectionsor spans of optical fiber as disclosed herein, such as one or moreregenerators, amplifiers, or dispersion compensating modules. In atleast one preferred embodiment, an optical fiber communication systemaccording to the present invention comprises a transmitter and receiverconnected by an optical fiber without the presence of a regeneratortherebetween. In another preferred embodiment, an optical fibercommunication system according to the present invention comprises atransmitter and receiver connected by an optical fiber without thepresence of an amplifier therebetween. In yet another preferredembodiment, an optical fiber communication system according to thepresent invention comprises a transmitter and receiver connected by anoptical fiber having neither an amplifier nor a regenerator nor arepeater therebetween.

Preferably, the optical fibers disclosed herein have a low watercontent, and preferably are low water peak optical fibers, i.e. havingan attenuation curve which exhibits a relatively low, or no, water peakin a particular wavelength region, especially in the E-band.

Methods of producing low water peak optical fiber can be found in PCTApplication Publication Numbers WO00/64825, WO01/47822, and WO02/051761,the contents of each being hereby incorporated by reference.

A soot perform or soot body is preferably formed by chemically reactingat least some of the constituents of a moving fluid mixture including atleast one glass-forming precursor compound in an oxidizing medium toform a silica-based reaction product. At least a portion of thisreaction product is directed toward a substrate, to form a porous silicabody, at least a portion of which typically includes hydrogen bonded tooxygen. The soot body may be formed, for example, by depositing layersof soot onto a bait rod via an OVD process.

A substrate or bait rod or mandrel is inserted through a glass body suchas a hollow or tubular handle and mounted on a lathe. The lathe isdesigned to rotate and translate the mandrel in close proximity with asoot-generating burner. As the mandrel is rotated and translated,silica-based reaction product, known generally as soot, is directedtoward the mandrel. At least a portion of silica-based reaction productis deposited on the mandrel and on a portion of the handle to form abody thereon.

Once the desired quantity of soot has been deposited on the mandrel,soot deposition is terminated and the mandrel is removed from the sootbody.

Upon removal of the mandrel, the soot body defines a centerline holepassing axially therethrough. Preferably, the soot body is suspended bya handle on a downfeed device and positioned within a consolidationfurnace. The end of the centerline hole remote from the handle ispreferably fitted with a bottom plug prior to positioning the soot bodywithin the consolidation furnace. Preferably, the bottom plug ispositioned and held in place with respect to the soot body by frictionfit. The plug is further preferably tapered to facilitate entry and toallow at least temporary affixing, and at least loosely, within the sootbody.

The soot body is preferably chemically dried, for example, by exposingsoot body to a chlorine-containing atmosphere at elevated temperaturewithin consolidation furnace. A chlorine-containing atmosphereeffectively removes water and other impurities from soot body, whichotherwise would have an undesirable effect on the properties of theoptical waveguide fiber manufactured from the soot body. In an OVDformed soot body, the chlorine flows sufficiently through the soot toeffectively dry the entire perform, including the centerline regionsurrounding centerline hole.

Following the chemical drying step, the temperature of the furnace iselevated to a temperature sufficient to consolidate the soot blank intoa sintered glass perform, preferably about 1500° C. The centerline holeis then closed during the consolidation step so that the centerline holedoes not have an opportunity to be rewetted by a hydrogen compound priorto centerline hole closure. Preferably, the centerline region has aweighted average OH content of less than about 1 ppb.

Exposure of the centerline hole to an atmosphere containing a hydrogencompound can thus be significantly reduced or prevented by closing thecenterline hole during consolidation.

As described above and elsewhere herein, the plugs are preferably glassbodies having a water content of less than about 31 ppm by weight, suchas fused quartz plugs, and preferably less than 5 ppb by weight, such aschemically dried silica plugs. Typically, such plugs are dried in achlorine-containing atmosphere, but an atmosphere containing otherchemical drying agents are equally applicable. Ideally, the glass plugswill have a water content of less than 1 ppb by weight. In addition, theglass plugs are preferably thin walled plugs ranging in thickness fromabout 200 pm to about 2 mm. Even more preferably, at least a portion ofa top plug has a wall thickness of about 0.2 to about 0.5 mm. Morepreferably still, elongated portion 66 has a wall thickness of about 0.3mm to about 0.4 mm. Thinner walls promote diffusion, but are moresusceptible to breakage during handling.

Thus, inert gas is preferably diffused from the centerline hole afterthe centerline hole has been sealed to create a passive vacuum withinthe centerline hole, and thin walled glass plugs can facilitate rapiddiffusion of the inert gas from the centerline hole. The thinner theplug, the greater the rate of diffusion. A consolidated glass perform ispreferably heated to an elevated temperature which is sufficient tostretch the glass perform, preferably about 1950° C. to about 2100° C.,and thereby reduce the diameter of the perform to form a cylindricalglass body, such as a core cane or an optical fiber, wherein thecenterline hole collapses to form a solid centerline region. The reducedpressure maintained within the sealed centerline hole created passivelyduring consolidation is generally sufficient to facilitate completecenterline hole closure during the draw (or redraw) process.Consequently, overall lower O—H overtone optical attenuation can beachieved. For example, the water peak at 1383 nm, as well as at other OHinduced water peaks, such as at 950 nm or 1240 nm, can be lowered, andeven virtually eliminated.

A low water peak generally provides lower attenuation losses,particularly for transmission signals between about 1340 nm and about1470 nm. Furthermore, a low water peak also affords improved pumpefficiency of a pump light emitting device which is optically coupled tothe optical fiber, such as a Raman pump or Raman amplifier which mayoperate at one or more pump wavelengths. Preferably, a Raman amplifierpumps at one or more wavelengths which are about 100 nm lower than anydesired operating wavelength or wavelength region. For example, anoptical fiber carrying an operating signal at wavelength of around 1550nm may be pumped with a Raman amplifier at a pump wavelength of around1450 nm. Thus, the lower fiber attenuation in the wavelength region fromabout 1400 nm to about 1500 nmn would tend to decrease the pumpattenuation and increase the pump efficiency, e.g. gain per mW of pumppower, especially for pump wavelengths around 1400 nm. Generally, forgreater OH impurities in a fiber, the water peak grows in width as wellas in height. Therefore, a wider choice of more efficient operation,whether for operating signal wavelengths or amplification with pumpwavelengths, is afforded by the smaller water peak. Thus, reducing OHimpurities can reduce losses between, for example, for wavelengthsbetween about 1260 nm to about 1650 nm, and in particular reduced lossescan be obtained in the 1383 nm water peak region thereby resulting inmore efficient system operation.

The fibers disclosed herein exhibit low PMD values particulary whenfabricated with OVD processes. Spinning of the optical fiber may alsolower PMD values for the fiber disclosed herein.

All of the optical fibers disclosed herein can be employed in an opticalsignal transmission system, which preferably comprises a transmitter, areceiver, and an optical transmission line. The optical transmissionline is optically coupled to the transmitter and receiver. The opticaltransmission line preferably comprises at least one optical fiber span,which preferably comprises at least one section of optical fiber.

The system preferably further comprises at least one amplifier, such asa Raman amplifier, optically coupled to the optical fiber section.

The system further preferably comprises a multiplexer forinterconnecting a plurality of channels capable of carrying opticalsignals onto the optical transmission line, wherein at least one, morepreferably at least three, and most preferably at least ten opticalsignals propagate at a wavelength between about 1260 nm and 1625 nm.Preferably, at least one signal propagates in one or more of thefollowing wavelength regions: the 1310 nm band, the E-band, the S-band,the C-band, and the L-band.

In some preferred embodiments, the system is capable of operating in acoarse wavelength division multiplex mode wherein one or more signalspropagate in at least one, more preferably at least two of the followingwavelength regions: the 1310 nm band, the E-band, the S-band, theC-band, and the L-band. In one preferred embodiment, the system operatesat one or more wavelengths between 1530 and 1565 nm.

In one preferred embodiment, the system comprises a section of opticalfiber as disclosed herein having a length of not more than 20 km. Inanother preferred embodiment, the system comprises a section of opticalfiber as disclosed herein having a length of greater than 20 km. In yetanother preferred embodiment, the system comprises a section of opticalfiber as disclosed herein having a length of greater than 70 km.

In one preferred embodiment, the system operates at less than or equalto about 1 Gbit/s. In another preferred embodiment, the system operatesat less than or equal to about 2 Gbit/s. In yet another preferredembodiment, the system operates at less than or equal to about 10Gbit/s. In still another preferred embodiment, the system operates atless than or equal to about 40 Gbit/s. In yet another preferredembodiment, the system operates at greater than or equal to about 40Gbit/s.

In a preferred embodiment, a system disclosed herein comprises anoptical source, an optical fiber as disclosed herein optically coupledto the optical source, and a receiver optically coupled to the opticalfiber for receiving the optical signals transmitted through the opticalfiber, the optical source having the capability of dithering, and/orphase modulating, and/or amplitude modulating, the optical signalgenerated by the optical source, and the optical signal is received bythe receiver.

It is to be understood that the foregoing description is exemplary ofthe invention only and is intended to provide an overview for theunderstanding of the nature and character of the invention as it isdefined by the claims. The accompanying drawings are included to providea further understanding of the invention and are incorporated andconstitute part of this specification. The drawings illustrate variousfeatures and embodiments of the invention which, together with theirdescription, serve to explain the principals and operation of theinvention. It will become apparent to those skilled in the art thatvarious modifications to the preferred embodiment of the invention asdescribed herein can be made without departing from the spirit or scopeof the invention as defined by the appended claims.

1. An optical waveguide fiber comprising: a central core regionextending radially outward from a centerline to a radius R₁ and having apositive relative refractive index percent, Δ₁ % (r) with a maximumrelative refractive index percent, Δ_(1,MAX), wherein Δ_(1,MAX)>0.6%; afirst annular region surrounding the central core region and extendingto a radius R₂ and having a non-negative relative refractive indexpercent, Δ₂ % (r), with a minimum relative refractive index percent,Δ_(2,MIN); a second annular region surrounding the first annular regionand extending to a radius R₃ and having a positive relative refractiveindex percent, Δ₃ % (r) with a maximum relative refractive indexpercent, Δ_(3,MAX); and an outer annular cladding region surrounding thesecond annular region and having a relative refractive index percent,Δ_(c) % (r); wherein Δ_(1,MAX)>Δ_(3,MAX)>Δ_(2,MIN)≧0; wherein therelative refractive index of the optical fiber is selected to provide aneffective area of greater than about 60 μm² at a wavelength of about1550 nm, a dispersion slope of less than 0.061 ps/nm²/km at a wavelengthof about 1550 nm, an attenuation at a wavelength of about 1550 nm ofless than 0.22 dB/km, and a zero-dispersion wavelength of less thanabout 1450 mn.
 2. The optical fiber of claim 1 wherein the relativerefractive index of the optical fiber is selected to provide adispersion slope of less than 0.07 ps/nm²/km at a wavelength of about1550 nm.
 3. (canceled)
 4. The optical fiber of claim 1 wherein thezero-dispersion wavelength is between about 1350 and 1430 nm.
 5. Theoptical fiber of claim 1 wherein the zero-dispersion wavelength is lessthan about 1430 nm.
 6. The optical fiber of claim 1 wherein theattenuation at a wavelength of about 1550 nm is less than 0.20 dB/km. 7.The optical fiber of claim 1 wherein the fiber has a dispersion at awavelength of about 1550 nm of between 6 and 10 ps/nm-km.
 8. The opticalfiber of claim 1 wherein the fiber has a dispersion at a wavelength ofabout 1550 nm of between 7 and 9 ps/nm-km.
 9. The optical fiber of claim1 wherein the central core region extends to a radius of between 3 and 5μm.
 10. The optical fiber of claim 9 wherein the first annular regionhas a width of between about 3 and 7 μm, and a midpoint of between 5 and8 μm.
 11. The optical fiber of claim 10 wherein the second annularregion has a width of between about 1 and 5 μm, and a midpoint ofbetween 10 and 12 μm.
 12. The optical fiber of claim 1 wherein the outerannular cladding region surrounds and is directly adjacent to the secondannular region, wherein the outer annular cladding region begins at R₃,and wherein Δ_(c) % (r)=0.
 13. The optical fiber of claim 1 wherein thecentral core region comprises a centermost portion extending from thecenterline to a radius of 1 μm, and a second portion surrounding anddirectly adjacent to the centermost portion, wherein the centermostportion has a maximum relative refractive index Δ_(AMAX), wherein thesecond portion has a maximum relative refractive index Δ_(BMAX), andwherein the absolute magnitude of the difference between Δ_(AMAX) andΔ_(BMAX) is greater than 0.2%.
 14. The optical fiber of claim 13 whereinΔ_(AMAM)>Δ_(BMAX).
 15. The optical fiber of claim 13 whereinΔ_(BMAX)>Δ_(AMAX).
 16. The optical fiber of claim 13 wherein theabsolute magnitude of the difference between Δ_(MAX) and Δ_(BMAX) isgreater than 0.4%.
 17. The optical fiber of claim 1 wherein the outerannular cladding region begins at R₃, wherein R₃ is between 11 and 18μm.
 18. A system comprising an optical source, a receiver, and theoptical fiber of claim 1 optically connecting the optical source and thereceiver, wherein the optical source is capable of generating opticalsignals in a wavelength range of 1530 to 1565 nm.
 19. An opticalwaveguide fiber comprising: a central core region extending radiallyoutward from a centerline to a radius R₁ and having a positive relativerefractive index percent, Δ₁ % (r) with a maximum relative refractiveindex percent, Δ_(1,MAX), wherein Δ_(1,MAX)>0.6%; a first annular regionsurrounding the central core region and extending to a radius R₂ andhaving a non-negative relative refractive index percent, Δ₂ % (r), witha minimum relative refractive index percent, Δ_(2,MIN); a second annularregion surrounding the first annular region and extending to a radius R₃and having a positive relative refractive index percent, Δ₃ % (r) with amaximum relative refractive index percent, Δ_(3,MAX); and an outerannular cladding region surrounding the second annular region and havinga relative refractive index percent, Δ_(c) % (r); whereinΔ_(1,MAX)>Δ_(3,MAX)>Δ_(2,MIN)≧0; wherein the relative refractive indexof the optical fiber is selected to provide an effective area of greaterthan about 60 μm² at a wavelength of about 1550 nm, an attenuation at awavelength of about 1550 nm of less than 0.22 dB/km, and azero-dispersion wavelength of less than about 1450 nm; and wherein thecentral core region comprises a centermost portion extending from thecenterline to a radius of 1 μm, and a second portion surrounding anddirectly adjacent to the centermost portion, wherein the centermostportion has a maximum relative refractive index Δ_(AMAX), wherein thesecond portion has a maximum relative refractive index Δ_(BMAX), andwherein the absolute magnitude of the difference between Δ_(AMAX) andΔ_(BMAX) is greater than 0.2%.
 20. The optical fiber of claim 19 whereinΔ_(AMAX)>Δ_(BMAX).
 21. The optical fiber of claim 19 whereinΔ_(BMAX)>Δ_(AMAX).